A conventional CC driving system that is employed in an active-matrix liquid crystal display device is disclosed, for example, in Patent Literature 1. CC driving is explained by taking as an example the content of disclosure in Patent Literature 1.
FIG. 20 shows a configuration of a device that realizes CC driving. FIG. 21 shows operating waveforms of various signals in CC driving of the device of FIG. 20.
As shown in FIG. 20, the liquid crystal display device that carries out CC driving includes an image display section 110, a source line driving circuit 111, a gate line driving circuit 112, and a CS bus line driving circuit 113.
The image display section 110 includes a plurality of source lines (signal lines) 101, a plurality of gate lines (scanning lines) 102, switching elements 103; pixel electrodes 104; a plurality of CS (capacity storage) bus lines (common electrode lines) 105, retention capacitors 106, liquid crystals 107, and a counter electrode 109. The switching elements 103 are disposed near points of intersection between the plurality of source lines 101 and the plurality of gate lines 102, respectively. The pixel electrodes 104 are connected to the switching elements 103, respectively.
The CS bus lines 105 are paired with the gate lines 102, respectively, and arrange in parallel with one another. Each of the retention capacitor 106 has one end connected to a pixel electrode 104 and the other end connected to a CS bus line 105. The counter electrode 109 is provided in such a way as to face the pixel electrodes 104 with the liquid crystals 107 sandwiched therebetween.
The source line driving circuit 111 is provided so as to drive the source lines 101, and the gate line driving circuit 112 is provided so as to drive the gate lines 102. Further, the CS bus line driving circuit 113 is provided so as to drive the CS bus lines 105.
Each of the switching elements 103 is formed by amorphous silicon (a-Si), polycrystalline silicon (p-Si), monocrystalline silicon (c-Si), and the like. Because of such a structure, a capacitor 108 is formed between the gate and the drain of the switching element 103. This capacitor 108 causes a phenomenon in which a gate pulse signal from a gate line 102 shifts the potential of a pixel electrode 104 toward a negative side.
As shown in FIG. 21, the potential Vg of a gate line 102 in the liquid crystal display device is Von only during an H period (horizontal scanning period) in which the gate line 102 is selected, and retained at Voff during the other periods. The potential Vs of a source line 101 varies in amplitude depending on an video signal to be displayed, but takes a waveform that inverts its polarity every H period centered on the counter electrode potential Vcom and reverses its polarity in an adjacent H period concerning the same gate line 102 (line inversion driving). Since it is assumed in FIG. 21 that a uniform video signal is being inputted, the potential Vs changes with constant amplitude.
The potential Vd of the pixel electrode 104 is equal to the potential Vs of the source line 101 because the switching element 103 conducts during a period in which the potential Vg is Von and, at the moment the potential Vg becomes Voff, the potential Vd shifts slightly toward a negative side through the gate-drain capacitor 108.
The potential Vc of a CS bus line 105 is Ve+ during an H period in which the corresponding gate line 102 is selected and the next H period. Further, the potential Vc switches to Ve− during the H period after the next, and then retained at Ve− until the next field. This switching causes the potential Vd to be shifted toward a negative side through the retention capacitor 106.
In the result, the potential Vd changes with larger amplitude than the potential Vs; therefore, the amplitude of change in the potential Vs can be made smaller. This allows achieving a simplification of circuitry and a reduction of power consumption in the source line driving circuit 111.